1. Field of the Invention
The present invention relates to a crystal growth equipment and a heat shield using in a silicon wafer process, and more particularly, to a crystal growth equipment using a Czochralski method and a length-adjustable and hybrid-angle heat shield.
2. Description of the Prior Art
The semiconductor develops from the 6-inch wafer, 8-inch wafer to the current 12-inch wafer. As the caliber of the wafer becomes larger, the crystal growth equipment and its technique should be upgraded continually.
In a wafer process, bulk single crystal silicon is the foundation of the silicon wafer, and the method of manufacturing the bulk single crystal silicon may be classified as the Czochralski method and the Floating Zone method, wherein, the Czochralski crystal growth equipment to extract the silicon single crystal is the most commonly used method nowadays.
FIG. 1 shows a sectional view of a Czochralski crystal growth equipment using a conventional heat shield. Referring to FIG. 1, a crucible 110 is disposed in a (Czochralski) puller 100, the crucible 110 is filled with semiconductor material melt 112, for example silicon melt, and a heater 102 is placed outside the crucible 110 to heat up the semiconductor material melt 112. A seed 116 is placed on the surface of the semiconductor material melt 112 in the puller 100. Pull up the seed 116, and the semiconductor material melt 112 attached to the seed 116 will be solidified into a single crystal 114. Otherwise, a support 104 is disposed outside the heater 102 in the puller 100, so that when a heat shield 118 is placed in the crucible 110, its cantilever 130 can be placed on the support 104 horizontally and its total weight be supported by the support 104.
The process of manufacturing the above-mentioned single crystal 114 is performed as follows: first put the semiconductor material into the crucible 110; melt the semiconductor material into the semiconductor material melt 112 at high temperature; then rotate the crucible 110 and contact the seed 116 with the semiconductor material melt 112; and then rotate the seed 116 in an opposite direction to that of the crucible 110 and pull it up slowly, and thereby the pulled-up part is solidified into the single crystal 114. When pulling up the seed 116 and the solidified single crystal 114, the heat shield 118 having an appropriate length to design a flow rate is provided to isolate the heat provided by the heater 102, at the same time the inert gas 140 above is fed into the puller 100 through a pumping unit (not shown) and flows into the space between the heat shield 118 and the single crystal 114 along the path. Therein, as the flow pitch is narrowed when the inert gas 140 passes through the bottom edge of the heat shield 118, the flow rate of the inert gas 140 is speeded up, and the oxide, for example the silicon oxide, resulted from the reaction on the semiconductor material melt 112 surface is taken away quickly from the silicon melt 112 surface. As the flow rate of inert gas 140 is very quick, the resulted oxide can be prevented from being melted back to the silicon melt 112 to produce a secondary pollution.
However, in the design of the path on which the inert gas 140 flows, if using the conventional heat shield 118 with a signal angle θ (i.e., the angle between the vertical wall 132 and the extension element part 136), a relatively large amount of argon gas is demanded to effectively cool the single crystal 114, and therefore the consumption of argon gas is rather great and the cost is high. Previously, efforts were made to aid the crystal growth by perforating the heat shield or changing the shape of the heat shield, but the process was too complicated; in addition, as the geometric shape of the furnace bodies are different by different factories, the installation position of the heat shield is influenced, so that a crucible can only be configured with heat shields with the same length, which burdens the cost indirectly.